CHM-1045 Lecture Notes - Fall 2017 Lecture 8 - Unified atomic mass unit, Carbon-12

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yellowtiger654

20 Sep 2018

School

FSU

Department

Chemistry and Biochemistry

Course

CHM-1045

Professor

Stephanie dillon

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Document Summary

The amu (atomic mass unit) was equal to 1/12 mass of carbon-12 atom. 6 protons + 6 neutrons = 12 grams: mass of carbon-12 = sum of the masses of protons and neutrons (1. 66 x 10-24g) x (1. 67 x 10-24g) = 1. 99 x 10-23g, 1 amu = 1. 66 x 10-24g. Mole: unit of entities, the amount of substance of a system which contains as many elementary entities as there are atoms in 0. 012kg of carbon-12: e(cid:374)tities (cid:272)a(cid:374) (cid:271)e: ato(cid:373)s, (cid:373)ole(cid:272)ules, io(cid:374)s, ele(cid:272)tro(cid:374)s . Avogrado"s nu(cid:373)(cid:271)er: 6. (cid:1004)(cid:1006)(cid:1006) x (cid:1005)(cid:1004)23 entities (6. 022 x 1023) x (1. 99 x 10-23g) = (cid:862)(cid:1005)(cid:1006)(cid:863) (shown in periodic table) Ex- a dozen bowling balls = mass of 120 lbs. A dozen eggs = mass of 2 lbs. A dozen people = mass of 1500 lbs. Periodic table has atomic weights equal to 1 mole of each element.

Related Questions

141. Calculate the mass in grams of one mole of each of the following (the mass of a single item is given in parentheses): electrons (9.10938 x 10-28 g), protons (1.67262 x 10-24 g), neutrons (1.67493 x 10-24 g), atoms of carbon-12 (1.992646 x 10-23 g), and doughnuts (74 g). Compare the mass of one mole of carbon-12 atoms to the sum of the masses of the particles that it contains. If the doughnut mentioned in this question were made entirely of carbon, how many atoms would it contain?

There are two stable isotopes of supposium (Su). Su-191=190.9609u(27.30%) Su-194=193.9633 u(72.70%) Compute the atomic mass ofsupposium.
a. 194.0 u b. 193.1 u c. 191.8 u d. 190.9 u e. 192.5 u

Which would not be found with a mass spectrometer.
a. the atomic mass of a single isotope of potassium
b. the number of stable isotopes of potassium c.the mass of aproton
d. the number of protons in potassium e. the relative abundance oftwo isotopes of potassium

How many protons, neutrons, and electrons are in 24 Mg2+?
12
a. 10 protons, 12 electrons, 24 neutrons b. 12 protons, 10electrons, 12 neutrons
c.12 protons, 12 electrons, 24 neutrons d. 24 protons, 10electrons, 12 neutrons
e. 12 protons, 12 electrons, 12 neutrons

1.The age of rocks is sometimes calculated from the measured excessof lead 206 atoms over the normal abundance. The uranium isotopeU-238 decays to lead-206.What is the percent abundance of lead-206if there aare 4.52 X 10^21 atoms of lead-206 in a 198 g sample ofore that is 2.58% lead? a. 27.7 b. 0.0202 c. 4.70 x 10^-3 d. 30.4e. 0.782

2. The average atomic mass of B is 10.80 u. Boron has only twostable froms 10
5 B(10.00 u) and 11
5 B (11.00 u). What is the natural percent abundance of B?
a. 1.0% b. 20% c. 75% d. 3.8% e. 80%

3. 57.7 g Ni contains how many atoms? a. 3.47x10^23 b.0.983 c. 1.24x 10^24
d. 6.13x10^23 e. 5.92x10^23

4. What mass of magnesium is necessary to make 10.5 g of magnesiumbromide if 1.04 g of magnesium makes 7.88 g of magnesiumbromide?
a. 7.89 g b. 1.39 g c. 79.9 g d. 3.66 g e. 1.58 g

5. How many atoms of lead are required to cover a 33.0 cm by 45.0cm area witha sheet of lead that is 0.140 mm thick? The density oflead is 11.35 g/cm3.
a. 1.42x10^26
b. 2.29x10^25
c. 6.86x10^22
d. 2.29x10^26
e. 6.86X10^23

6. The natural abundance of calcium in the earth's crust is 3.4% bymass. How many calcium atoms are present in a 1.50 g sample of theearth's crust?
a. 7.7x10^22 b. 7.7x10^20 c. 3.1x 10^22 d.6.6x10^23 e.5.1x10^20

9.Rubidium possesses two stable forms and has an average mass of85.5. 85Rb has a mass of 84.9 and a percent abundance of 72.2%.What is the mass of the other form of Rb?

a. 85.7 u
b. 88.3 u
c. 86.1 u
d. 89.4 u
e. 87.1 u

10. Which is the more abundant isotope, CI-35 or CI37?
a. CI-17
b. CI-37
c. The two isotopes are equal in balance
d. CI-35
e. A third unstable isotope is more abundant

11. An element has 5 stable isotopes. The mass and percentage ofeach are:
69.9243 20.52%
71.9217 27.43%
72.9234 7.76%
73.9219 36.54%
75.9214 7.76%
The element is which of the following
a. Se b. Ge c. Ga d. As e. Zn

12. Lead-206 has a relative abundance of 23.6%. What sized block oflead (in cubic centimeters) will contain 8.34x10^21 atoms oflead-206? The density of lead is 11.35 is g/cm3.
a. 0.253
b. 0.0107
c. 1.07
d. 12.1
e. 0.330

13. When decomposed chemically, 73.0 grams of a sample of HCIproduce 71.0 g of Cl2 and 2.0 g of H2, while 34.0 g of a sample ofH2s produce 32.0g of S and 2.0g of H2. This is an example of theLaw:
a. of Definate Proportions
b. E=mc^2
c. of multiple proportions
d. of Conservation of Mass
e. none of these

CHM-1045 Lecture Notes - Fall 2017 Lecture 8 - Unified atomic mass unit, Carbon-12

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